Herbs for a Toronto Roof Garden

I have a roof garden downtown Toronto, Ontario, Canada--with 14 containers (each 2'x2.5'). It gets full sun from sun up to sun down. It is also enclosed with chicken-wire. In the past I have grown tomatoes with success, however I am wondering if there is some crop that this environment is optimally suited to. In addition, if it is not too practically oriented, I would ideally like to find some crop that I could sell or use. I currently purchase Tribulus capsules from the health-food store and these are expensive. Could I grow that? What about sweetgrass--I could use that. What about green-tea? I suspect this would not work, but I thought I would ask. Similarly, what about ginseng?

Tribulus is an annual vine and it likes moist soil that should not be too hard to supply. The problem with roof-top gardens is the wind, but since you grew tomatoes successfully you must have solved the problem or are lucky to have a sheltered roof.
Sweetgrass should do just fine and it would even over-winter out of doors in zone 5 Toronto.
By green tea I presume you mean Camellia sinensis. It is only hardy to zone 7 and would have to be over-wintered indoors in a cool room.
Ginseng might work if you get some deciduous forest soil, use rain-water to water it and make sure it is shaded and sheltered from winds. In the winter you would havee to insulate the pot well so that the soil in it does not get too cold. Siberian ginseng is hardy to zone 3 and could survive a zone 5 winter in a pot, but the zone 4 American ginseng needs it warmer.